You really cannot deal Lester right now. You dont sell a player when it's value is at its lowest, especially when he isnt terribly expensive to begin with. Beckett, OTOH, might not recoup his value as he is getting older and his stuff has dropped off the past few seasons. This yr, his command isnt what it used to be.
The sox have a few pieces that could bring back something of value. Aceves, Padilla, Atchison, and Miller would all bring back something at the deadline since pen pitching is the most traded commodity at the deadline every yr. And there is no guarantee all of those guys are back next yr
Cody Ross is on a 1 yr deal. His OPS is at .882 with big power and he is hitting both home and away. If he continues like this, he's getting a 3-5 yr deal in the offseason at $8-10 mil per yr money. The sox have Kalish behind him, so he is an easy choice to move.
The sox also have to deal Big Papi. The sox cannot actually offer him arbitration. Due to the new CBA, they can only offer him a 1yr $12 mil deal through the arb process instead of a continued ratcheting up of his value on a 1yr basis. That means he will walk, and if his comments of late tell us anything, I think he would walk even if the sox could offer him 1 yr $16 mil through the modified arb process. And through that process, their draft compensation is minimized, so they are gonna have to get something for him.